G. David Baxter and Suzanne M. McDonough
10.1 Overview
10.2 Electrical stimulation of tissue 10.3 Electrical stimulation for pain relief 10.4 Electrostimulation of muscles 10.5 Laser therapy
10.6 Ultrasound therapy 10.7 Evidence-based practice 10.8 Summary and conclusions References
Based upon these fibre types, a variety of effects are pos-sible with electrical stimulation of a single nerve:
1. Intensity of stimulation. Large diameter, myelinated fibres have a lower threshold for activation, and there-fore are most easily stimulated with lower stimulation intensities. In Figure 10.2 it can be seen that the largest diameter fibres are motor fibres, followed by the large diameter sensory fibres. However, in practice when sur-face electrodes are placed on the skin, normally these large diameter sensory fibres are activated first as they are closer to the stimulating electrodes than the motor nerves. Intensities are usually set using arbitrary units on most commercially available stimulators – typically with a ‘wheel’ control or similar – but intensity essen-tially refers to the magnitude of the current flow and is specified in milliamps (mA).
2. Frequency of stimulation. This is specified in pulses per second – or Hertz (Hz) – and is limited physiologically by the absolute refractory period of the nerve, that is, how long it takes to recover from the production of an action potential, and be ‘ready’ for the next stimulus.
It is longer for slowly conducting nerve fibres, which have a smaller diameter, and consequently these fibres respond preferentially to low frequencies.
3. Pulse duration. This is specified in milliseconds or microseconds; the shortest (microsecond) pulse dura-tions preferentially stimulate sensory fibres, while the longer pulse durations preferentially stimulate motor nerve fibres. The reason why the large diameter sensory fibres are stimulated first can be explained by the relative proximity to the surface electrodes.
There is a variable threshold for stimulation of different types of nerve fibre, which depends upon the intensity (strength), pulse duration of the applied stimulus and the distance from the stimulating surface electrodes: this is illustrated schematically in Figure 10.3. Apart from the dif-ferent slopes of the curve for difdif-ferent types of nerve, denot-ing sensory modalities versus motor activation, it is also important to note that for longer pulse durations, lower stimulus intensities are required to stimulate a nerve.
10.2.3 Application of electrical stimulation For stimulation of muscle or nerve, two electrodes are applied. While, by convention, the black electrode is the cathode, and the red electrode is the anode, in the applica-tion of biphasic currents, polarity is not critically important.
Selection of sites for stimulation or electrode placement will depend upon the desired effect of stimulation and include: over the bulk of the muscle, motor points, over peripheral nerves, acupuncture points, over spinal nerve roots, or directly to the painful area.
Selection of electrode type will depend upon a variety of considerations; the two principal types of electrode avail-able are carbon electrodes, which require application of gel
•
Motor nerve fibres (myelinated Aαfibres)•
Large diameter (myelinated) sensory fibres, including Type II, Aβ‘touch’ pressure receptors•
Thinly myelinated fibres, Type III (Aδ)-mechanothermal receptors•
Unmyelinated nociceptive fibres subserving pain, Type IV-unmyelinated (diffuse pain)Pulse duration Notes:
(i)
(ii)
(iii)
The figure represents a schematic of a typical electrostimulation waveform: while it is asymmetric, the positive and negative components are equivalent and thus overall there is no net direct current effect.
Pulse Amplitude represents the intensity of the stimulation; when the intensity of the stimulation is increased by the therapist, the amplitude is increased, Pulse Duration (coupled with the number of pulses per second) is a key parameter in determining the effects of stimulation (e.g. muscle stimulation or pain relief).
Pulse amplitude
Figure 10.1 Pulse waveform with key parameters.
Type Characteristics
Aα Motor fibres
Diameter 13–20 μm Speed
80–120 ms–1
Aβ
Sensory fibres Mechanoreceptors Low-threshold
Diameter 6–12 μm Speed 35–75 ms–1 Aδ Sensory fibres
Mechanothermal High-threshold
Diameter 1–5 μm Speed 5–35 ms–1
C Nociceptors
Diameter <1.5 μm Speed <2 ms–1 Figure 10.2 Peripheral nerve: key characteristics.
to transmit electrical current, as well as tapes for attachment onto the skin, and reusable, pre-gelled, self-adhesive elec-trodes. While the former are less costly, the latter tend to be more commonly used clinically, are less time-consuming to apply and are more convenient for application by the owner or carer.
10.3 Electrical stimulation for pain relief
10.3.1 Overview
Electrical stimulation has been used for pain relief since ancient times; however, until the publication of the original paper outlining the pain-gate theory by Melzak and Wall (1965), electrostimulation for pain relief (or electroanalge-sia) was not widely accepted outside the profession. Based upon initial work by Wall and Sweet (1967) (and others) so called transcutaneous electrical nerve stimulation (TENS) for pain relief has become a popular alternative to pharma-cological methods of pain relief, particularly after the intro-duction of the first portable and affordable TENS units in the 1970s (see Walsh 1997).
While the term TENS could arguably be applied to any form of electrostimulation, its use has become limited to the description of electrostimulation for pain relief using small, compact portable units. Equally, while there are vari-ous types of electrostimulation device available, based upon different waveforms or methods of application, ranging from interferential therapy to H-wave therapy, the underly-ing principles are identical.
10.3.2 Mechanisms of action
While other physiological effects are possible with electrical stimulation (such as increases in blood flow and localised blocking of peripheral nerve fibres), the two main mechan-isms by which electrostimulation produces pain relief are:
segmental inhibition through pain-gating mechanisms, and via descending inhibitory mechanisms (see Baxter & Barlas 2002). The first of these relies on the selective stimulation of larger diameter fibres in peripheral nerves, which in turns helps to ‘block’ nociceptive activity in smaller afferents at segmental level (see Figure 10.4). For this, so-called con-ventional TENS is used, based upon higher frequency stimu-lation, coupled with longer pulse durations.
Descending inhibitory effects are also possible, based upon the release of endogenous opiate-like substances, in response to more intense levels of stimulation at lower pulse frequencies. Because of the similarity to (needle) acupuncture, this type of TENS is frequently termed acupuncture-like TENS. While the effects of opiate release are widespread, one of the primary sites of action is at the relevant segmental level, where opiate interneurons medi-ate the pain-relieving effects.
10.3.3 Indications: clinical use of electroanalgesia
Electrostimulation can be used for the relief of pains of various aetiologies, including:
•
Acute pain associated with surgery (post-operative pain), ligament sprains, fractures and with labour painStimulus amplitude (mA)
Pulse duration (μs) 40
1 10 100
Motor
Sensory 30
20
10
Noxious
Figure 10.3 Nerve stimulation: relevance of pulse characteristics.
Large diameter fibres
Peripheral input
Small diameter fibres
Notes:
(i)
(ii)
(iii)
(iv)
The figure illustrates as a schematic the main elements of the pain control mechanisms underpinning pain relief using electrotherapeutic agents.
Sensory input from the periphery reaches the relevant segmental level of the spinal cord, where this is transmitted to rostral levels of the nervous system via T-Cells or wide dynamic range cells.
The relative degree of activity in large and small diameter fibres determines the activation of inhibitory mechanisms via interneurons in the substantia gelatinosa (also called SG-cells); these can block the passage of nociceptive information through the spinal cord. (Called segmental inhibition or pain-gating mechanisms).
Parallel activation of central mechanisms stimulate descending inhibitory control mechanisms through the activation of opiate interneurons, which modulate the processing of nociceptive information through the spinal cord.
T-cell Interneuron
Interneuron Central control systems
Segmental level
Thalamus
Figure 10.4 Pain control mechanisms.
10.4 Electrostimulation of muscles
The preferred term for electrical stimulation applied to effect contractions of muscle is neuromuscular electrical stimulation or NMES (McDonough & Kitchen 2002). The terms functional electrical stimulation (FES) or functional neuromuscular stimulation (FNS) are used to describe therapy using units that aim to ‘mimic’ the stimulation patterns of intact nerves, in cases where the nerve supply is damaged, e.g. peripheral nerve damage. Other terms, thera-peutic electrical stimulation (TES) and electrical stimula-tion are sometimes used, but typically refer to devices that are designed to elicit sensory effects only.
It is important to note that the waveforms used in TENS and NMES are essentially the same; furthermore the cur-rent capacities (i.e. the electrical intensities produced by available units) are identical. The differing effects of each type of therapy are based upon the selection of appropriate stimulation parameters, and particularly, pulse duration, or width, and pulsing frequency; this is reflected in the design of casing and dials of units to allow manipulation of wave-form characteristics (Figure 10.1; Table 10.1).
•
Chronic musculoskeletal pain, including spinal pain and neuralgiaWhile electrostimulation can be used to treat most types of pain, it tends to produce best results in cases of more localised pain, of more moderate intensity, and where the site of pain is more superficial. More variable results are reported with more severe, widespread and deeply seated pain.
10.3.4 Principles of application
Before initial application, the patient should be adequately assessed and a diagnosis obtained. The patient should be checked for contraindications, and where possible the site or area of application should be tested and cleansed to improve conductivity. For initial treatments, time of appli-cation should be kept relatively short e.g. 15 –20 min, to reduce any anxiety and to familiarise the animal with the sensations associated with stimulation. Treatment should generally be initiated with ‘conventional TENS’ as this is more comfortable and is therefore easily tolerated. At sub-sequent sessions, treatment time can be increased up to one hour at a time, and where appropriate, ‘acupuncture-like TENS’ can then be introduced or trialled.
Electrode placement (Figure 10.5)
TENS can be applied at a variety of sites, and some degree of experimentation may be necessary to determine the optimal site for electrode placement for effective pain relief.
The most common site of electrode application is directly over the area of pain, with the electrodes placed to ensure that the majority of current, and therefore nerve stimula-tion, will pass through the site of pain. Alternatively, the TENS electrodes can be placed (proximally) directly over the relevant peripheral nerve that supplies the affected area, or over the relevant spinal nerve roots. In the latter case, the electrodes are placed lateral to the spine, so they are over the relevant spinal nerve roots. The effectiveness of both of these types of application is dependent upon an adequate knowledge of anatomy, especially relating to nerve supply of relevant structures (e.g. relevant dermatomes or myotomes for the animal patient).
Electrodes can also be placed over acupuncture, motor and trigger points. For therapists wishing to gain the benefits of acupuncture, use of acupuncture points for electrical stimulation can represent an effective and practical alterna-tive to needles, which may be difficult in some animal patients, or limited by regulation or scope of practice. Alternatively, there is a high degree of correspondence between acupunc-ture and ‘trigger points’, which can also be used as an elec-trode placement site for electrostimulation, where these are identified upon palpation. Finally, motor points represent the best site for the treatment of muscle pain; when using acupuncture-like TENS, electrodes should be placed over the relevant muscle/appropriate myotome, and intensity increased until a muscle contraction is obtained.
Figure 10.5 Electrode placement for transcutaneous electrical nerve stimula-tion (TENS) in a dog 3 days after hemilaminectomy surgery. Four electrodes are used close to the surgical site. Note similar placement of electrodes could also be used for neuromuscular electrostimulation (NMES); however care should be taken to avoid the surgical site when using NMES settings.
10.4.1 Mechanisms of action
Skeletal muscle fibres can be contracted by conscious (voluntary) or automatic control from the central nervous system; electrical currents can also ‘artificially activate’
muscle fibres by activation of the peripheral nerve to the muscle. There are different types of skeletal muscle fibres, which produce different types of muscle work. Type I are red in colour, slow twitch and relatively stable; they are activated at relatively low levels of muscle activity, over rela-tively long durations. Because of their aerobic metabolism, they fatigue slowly. Type IIB muscle fibres are white in colour, fast twitch, and produce muscle power. While they provide high levels of muscle activity, because of their anaerobic metabolism, they fatigue quickly and thus are only active for relatively short periods. Depending upon the pattern of the electrical stimulation, either or both types of fibre can be activated.
10.4.2 Indications
Electrical stimulation has been used for strengthening of normal muscle, however the evidence for electrical stimu-lation over voluntary exercise is limited. In atrophied muscles, the evidence from human studies is variable: in quadriceps and abdominal muscles, the evidence is conflict-ing, while there is some evidence of benefit in the muscles of the lumbar spine. Electrical stimulation has also been used for muscle stimulation in neurological damage, promoting motor recovery and strength, in the treatment of subluxa-tions (in the early stages of recovery) and for the reduc-tion of muscle spasticity. In animals, the primary use is the treatment of muscle atrophy, to underpin re-education of muscle function, and muscle strengthening (Figures 10.6 and 10.7). As in humans, muscle strengthening in muscle atrophy resulting from neurological lesions has also been successfully achieved with electrical stimulation. Suggested uses have also included strengthening of muscles and promotion of muscle recovery post-operatively, where resolution of oedema has also been reported; in such cases application near the incision site should be avoided (although TENS can be applied close to the wound for pain relief, as in Figure 10.5).
10.4.3 Principles of application
Before electrode application, the animal’s hair should be clipped to lower resistance to passage of current, and
if possible, the area of application should be washed with soap and water (alcohol should be avoided). There are two techniques used to locate electrodes. The first is placement of a primary electrode over the motor point which can be located using a probe electrode, with the current pulsed at 1 Hz. Once the optimal site for muscle stimulation has been identified, this should be marked where possible with an indelible marker. A second dispersive or indifferent elec-trode must be placed elsewhere on the body part, at a convenient location near the muscle being treated. This electrode should be larger, so that the current density across it is lower and it is therefore unlikely to elicit either motor or sensory responses. Alternatively, electrodes of a similar size can be placed at either end of a muscle belly so that the bulk of the muscle is covered. In this method, location of the motor point is not important, however, in order to identify where best to place the electrodes it is important to have a good knowledge of the anatomy of the muscle.
If using this technique, electrodes should be large enough to cover the bulk of the muscle (without touching one another); the standard-sized electrodes which come with most battery-powered and line-powered units are likely to be too small for larger animals.
Table 10.1 Comparison of TENS and NMES Electrostimulation
Neuromuscular electrostimulation Transcutaneous electrical stimulation
Effects
Muscle stimulation Pain relief
Pulse duration
<1 ms (200–600 μs) 200μs
50μs
Pulse frequency
>50 Hz
<20 Hz
>100 Hz Pulse amplitude
Sufficient intensity to provide muscle contraction Sufficient intensity to provide muscle contraction
‘Strong but comfortable’
Figure 10.6 Electrode placement for neuromuscular electrostimulation (NMES) in a dog 3 days after hemilaminectomy surgery, electrodes are moved until appropriate muscle contraction is obtained, then taped into place for the treatment.
uterus should be observed with electrical stimulation, as well as no application over indwelling stimulators or similar devices. Electrical stimulation should not be applied over the eyes or gonads. Other areas in which caution should be exercised include infected or broken skin (although some forms of electrical stimulation can be used as a means of stimulating wound repair), as direct application may exacerbate existing conditions.
10.5 Laser therapy
10.5.1 Overview
Laser is an acronym for ‘light amplification by stimulated emission of radiation’; it is a form of electromagnetic radi-ation in the visible and near visible part of the spectrum.
Lasers have found a variety of applications in veterinary medicine: their uses range from surgical to diagnostic devices. Low intensity laser therapy (also known as low level laser therapy, laser biostimulation, or more simply laser therapy) may be defined as the use of low power – typically 500 mW or less – laser sources and superluminous diodes (similar in many respects to laser diodes, but lacking the property of coherence) for the treatment of medical condi-tions; it is based upon athermic tissue reactions.
10.5.2 Mechanisms of action
The basic interaction underlying laser therapy is the absorp-tion of light in irradiated tissue by specific biomolecules.
These are known as chromophores, typically found within the cell mitochondria. Based upon this absorption, light energy is transformed into biochemical energy. Follow-ing this initial absorption, there are a variety of secondary reactions, which result in modulation of cellular functions, and typically the stimulation of tissue-repair mechanisms.
In addition, laser irradiation may also help reduce pain when used at appropriate treatment parameters. Absorp-tion of light is the key to the basis of the effectiveness of laser therapy: thus while tissue penetration is often quoted in terms of millimetres, it should be realised that tissue absorption is more important.
10.5.3 Specific effects of therapy
A variety of effects of laser irradiation have been reported under controlled laboratory conditions including altered nerve conduction, changes in blood flow circulation, and stimulation of angiogenesis. Neurochemically, laser irradiation has been shown to increase the metabolism of endogenous opiates, acetylcholine and serotonin. At cellular level, laser irradiation has been shown to enhance the production of ATP within cells, and thus mediate or modulate a variety of other events including release of growth factors, cytokine reactions and cell replication; the ultimate effect of these events is acceleration of delayed tissue healing. This is the primary, or cardinal effect, of laser therapy, and thus the term laser photobiostimulation (or Electrostimulation parameters should be set to obtain
the best effect from each treatment session; as part of this, it is worth taking time to identify the optimum placement sites for electrodes. As far as is possible, regular treatment (e.g. every other day) is preferable, with the length of each treatment session set to allow adequate periods of stimulation interspersed with adequate ‘recovery periods’.
Treatment should be initiated with stimulation at 60–100 Hz, with an on:off ratio of at least 1:3 (i.e. 5:15 s) set to induce fatigue within the stimulated muscle. The intensity should be adjusted to provide the strongest contraction possible within the animal’s tolerances. However, it has been suggested that to strengthen muscle, it may be neces-sary to use muscle contractions of the order of 25% and 50% of maximum voluntary isometric contractions (MVIC) to obtain clinically meaningful outcomes (Alon 2005).
Treatment should be started with stimulation of 8–15 con-tractions per session, with sessions provided 3–5 times per week. Subject to adequate response, the treatment should be continued over 3–5 weeks of training.
10.4.4 Safety, contraindications and precautions There are limited reports of side effects or adverse reac-tions with electrical stimulation in humans. However, the common contraindication of treatment over the pregnant
Figure 10.7 Electrode placement for neuromuscular electrostimulation (NMES) in a horse with disuse atrophy secondary to non-weight bearing lame-ness for 2 months. The upper electrode is over the triceps muscle, the lower electrode is at the top of the splint (partially tucked in) over the head of the extensor carpi radialis.
simply ‘biostimulation’) is frequency used to describe the therapy, especially in the USA.
10.5.4 Indications: conditions treated
Laser therapy finds wide application in the treatment of a variety of conditions. These principally include:
•
Wounds and ulcers: Pressure sores, chronic wounds/delayed wound healing, diabetic ulceration, burns, skin abrasions
•
Acute injuries/trauma: Tendon and muscle tears/haematoma, ligament sprains, fractures, subluxations, and various types of sporting and soft tissue injuries
•
Musculoskeletal conditions: repetitive strain injuries, rotator cuff tears, carpal tunnel syndrome, complex regional pain syndrome/reflex sympathetic dystrophy, fibromyalgia and temporomandibular joint pathologies•
Inflammatory conditions (acute and chronic): Tend-initis, bursitis, myositis, fascitis, synovitis•
Arthritis and related conditions: Rheumatoid arthritis (and other autoimmune diseases), osteoarthritis, chon-dromalacia patella, calcifications (e.g. bone spurs) 10.5.5 Treatment principles: devices and specifying parametersContemporary laser treatment devices used in veterinary practice are based upon either single (pen style) or multiple source diode units, the latter being available as fixed (commonly called clusters) or flexible units (typically based upon rubberised units). The output of the unit – radiant power output – should be specified in milliWatts (mW), and is fixed by the selection of the treatment ‘head’. Control units allow setting of treatment parameters, which might include time of irradiation/treatment, and setting of puls-ing frequency (Table 10.2). The treatment time is import-ant in determining the dosage of treatment: energy in Joules (J) is calculated as:
Energy (J) =
Thus a 33-s treatment with a 30 mW unit will provide a treatment dosage at the irradiated point of approximately one Joule (0.99 J). This means of specifying dosage is useful
Radiant power (mW) ×Time (s) 1000
for routine clinical treatment of points on intact skin. For the treatment of open wounds, it is more appropriate to use energy density(also called radiant exposure, based upon the area irradiated), which is also typically used in research reports on wound healing. For this, the area of the wound is calculated (in cm2), as well as the total energy in joules delivered over the surface of the wound.
Energy density is then calculated as:
Energy density (J/cm2)=
In such cases, treatment should be initiated at dosages of 4 J/cm2 and progressed depending upon response to treatment.
Pulsing frequencies may also be selected on some machines: in such cases, lower pulsing frequencies (e.g.
<20 Hz) are typically used in more acute conditions, while higher pulsing frequencies (hundreds to thousands of Hz) are typically used in the treatment of chronic conditions and open wounds.
Effectiveness of routine clinical treatment is dependent upon systematic and comprehensive treatment of sites: this starts with direct application to lesion/wounds or site of pain (using contact technique where possible, i.e. intact skin), relevant nerve roots and trunks, as well as trigger or tender points for pain management, and acupuncture points if appropriate. In treatment, especially of wounds and burns, lymphatic and blood vessels can also be usefully targeted for treatment.
10.5.6 Safety, contraindications and precautions
The safety of laser therapy is well established: there are limited reports of side effects or adverse reactions; in humans, there are extremely rare reports of nausea follow-ing irradiation over nerve roots, or sensations (tfollow-inglfollow-ing) during treatment.
Contraindications to treatment principally include active or suspected carcinoma, or areas of haemorrhage; care should also be taken in performing treatment near the eyes, even though the risk of eye damage is limited. Treatment over the pregnant uterus is also contraindicated.
Energy (J) Wound area (cm2)
Table 10.2 Laser therapy: parameters Wavelength
600 –1000 nm
Red (visible) in 600 nm range
Infrared (invisible) >700 nm
Power milliWatts (mW)
Typically: (for single sources) 30 –500 mW for animal therapy May be higher for multisource arrays
Dosage Joules (J)
Typically: Up to 30 J per point in animal therapy
Joules per cm2(J/cm2)
Typically: 4 J/cm2over open wounds Pulsing
May be Continuous Wave (CW) If pulsed, settings can range from 1 Hz to 20 000 Hz (20 kHz)
In parallel with improved or accelerated wound healing, commonly observed benefits of treatment include reduced oedema, pain relief and improved patterns of sleep.
10.5.8 Applications in rehabilitation: practical considerations
Stimulation or restoration of wound-healing processes represents a common effect in all tissue types, and coupled with the pain-relieving effects of treatment, laser therapy thus finds wide application in animal therapy. In compar-ison with other electrophysical modalities, such as ultra-sound or electrostimulation, this combination of increased healing plus pain relief, coupled with the athermic nature of its effects (with less risk of burns or exacerbation in acute stages), means that laser therapy is often the modality of choice. However, as in humans, laser therapy represents only one element of comprehensive physiotherapy treat-ment and rehabilitation for the animal patient. While laser treatment can be safely and effectively combined with most other modalities and integrated easily with other treatment approaches, it is important to recognise the relevance of the sequence of application with other modalities. In particular, thermal modalities can have a significant influence on the effectiveness of therapy, given their effects upon blood flow, and thus the ‘saturation’ of blood chromophores in the tissue. Where tissue perfusion is reduced, as in cryotherapy, the distribution of absorption of laser energy will be affected, so that chromophores in deeper structures will be targeted by treatment. This might well be a useful treatment strategy in larger animals in which the lesion or target tissue is deeply sited. In contrast, in cases of application of laser following tissue heating, the effects of treatment will be much more systematic than local, given the absorption by chromophores within the blood.
Laser devices (single diodes) can also be used to stimulate acupuncture points as an alternative to needles. Advantages associated with such ‘laser acupuncture’ include the fact that it is non-invasive and therefore easier and safer to apply; avoids problems with needle phobia; and although it requires reduced training, it is claimed by many thera-pists to be just as effective as needle treatment in some cases.
10.6 Ultrasound therapy
Therapeutic ultrasound (US) is one of the most commonly used electrotherapeutic modalities. It is based upon the application of longitudinal sound waves to the body for a therapeutic effect, i.e. molecules of the tissues treated oscil-late in the same direction as the sound wave (see Table 10.3 for parameters).
10.6.1 Mechanism of action
US has been shown to have a direct effect upon cells, and, in the laboratory, to stimulate healing. The effect can be either 10.5.7 Treatment of wounds: key principles
In treating wounds, dosages over the wound surface should be kept relatively low (4 J cm2). In addition, systematic treatment is essential to success. Treatment approaches can vary, depending upon the treatment unit available (i.e. sin-gle diode probe or treatment head versus a multisource array), and upon the size of wound. Treatment of larger wounds in large animals might only be feasible with multi-source arrays, while in smaller animals, single diodes might be necessary.
Wound treatment is a two-stage process, including the treatment of the wound bed (using non-contact technique, distance of approximately 1 cm), followed by contact treat-ment of the intact skin around the wound margin, approx-imately 1 cm from the edges of the wound. As already indicated, lymphatic vessels can also be usefully treated to enhance the effectiveness of therapy.
Laser treatment of wounds should be harmonised with concomitant treatment procedures; e.g. any necessary debridement of the wound should be performed before applying laser treatment. For treatment of the wound bed of a larger wound, if only a single diode probe is available, care should be taken to ensure that as far as possible, a standardised dosage is applied across the whole of the wound. For this, some therapists use a grid or ‘chess board’ approach, based upon the same principles used for assessment with the probe applied to squares of 1 cm ×1 cm. Alternatively, ‘manual scanning’ can be used, similar to ultrasound, however, in such cases it is difficult to standardise the treatment. However, for larger wounds, treatment with a single diode can be prohibitively time-consuming and thus multisource arrays, or in rare cases, scanner devices, are preferred as they provide the ability to cover an extensive area with one shot (typically 12–20 cm2 coverage). Treatment of the wound margin represents an essential second phase of treatment, applying laser through integral/patent skin using ‘in-contact’ principles with appropriate dosages (at least 1–2 J per point).
Infected wounds are typically regarded as a ‘relative’
contraindication to laser treatment, based upon fears of photobiostimulation of the infection. However, stimula-tion of the host response is frequently overlooked as the primary effect of treatment; based upon this, the presence of infection can represent an indication for laser treatment.
However in such cases, aseptic technique is essential, as part of which a pragmatic approach such as the use of ‘Clingfilm’
wrap either over the treatment head, or wrapped around the wound can provide an effective aseptic barrier. As already indicated, treatment should be initiated at a dosage of 4 J/cm2and progressed, depending upon response. While overdosing is theoretically possible, therapist’s time is a more practical consideration and thus treatment dosages above 12 J/cm2are commonly used, thus decreasing treat-ment time, particularly with larger wounds.